A common prior art method for forming glass fibers for use in wool products, such as insulation materials, is the use of a rotary process. Glass in its molten state is forced through the orifices in the peripheral wall of a centrifuge or spinner to create streams of molten glass. Thereafter, the streams are further attenuated into glass fibers of smaller diameter by the action of gases discharged downwardly in an annular or cylindrically shaped gaseous flow circumferentially positioned relative to the spinner. Some prior art rotary processes use an annular combustion chamber positioned around the spinner to produce high temperature, high velocity, gases of combustion which are discharged downwardly in a circumferential flow. In other prior art methods, air or steam blowers are utilized either alone or in combination with burners to provide a downward or pulling force.
Krakauer et al. U.S. Pat. No. 3,347,648 discloses the use of a water spray after attenuation and commingling of the filaments to accelerate cooling the filaments whereby resin or binder may be applied sooner. Contrary to the present invention, the rotary process disclosed in Krakauer et al. uses a high velocity, high temperature external burner positioned to discharge a hot high temperature gaseous blast downwardly closely adjacent the spinner to attenuate the glass fibers. The Krakauer et al. water supply pipe applies water to the fibers after they have turned down and fiber commingling has occurred.
Textile fibers are generally longer and stronger than wool fibers produced by prior art rotary processes. For the purposes of this invention, textile fibers are fibers of sufficient length and strength to be used in textile materials, for reinforcing purposes in fiber reinforced plastics and as reinforcing fibers in such products as roofing shingles.
After the longer length textile fibers are manufactured they often are cut into shorter lengths for certain reinforcing applications.
In a prior art rotary process, where rotary glass fibers are manufactured for non-textile applications, the tensile strength of the glass fibers is normally considerably lower than 50,000 p.s.i. (35.1 kg/sq. mm.). Textile fibers should have tensile strengths of 150,000 p.s.i. (105.3 kg/sq. mm.) and preferably 300,000 p.s.i. (210.7 kg/sq. mm.).
Attempts have also been made in the prior art to produce textile fibers by the rotary process. The high fiber production rate of a rotary process is much greater than the fiber production rates of non-rotary processes. One prior art attempt at a rotary process is shown in U.S. Pat. No. 3,900,302. These prior art attempts to form textile glass fibers by the rotary process have not, to the knowledge of the present inventors, been successful. Accordingly, the primary purpose of the present invention is to form satisfactory textile mineral fibers, such as textile glass fibers, by a rotary process.